Brush seal and the like



March 17, 1959 R, o, PETERSON 2,878,048

' BRUSH SEAL AND THE LIKE Filed March 18, 1954 2 Sheets-Sheet 1 INVENTOR. PUBf/V 0. PE TE/R50/V A T TOIQNfYS- March 17, 1959 v R. o. PETERSON BRUSH SEAL AND THE LIKE N TOR.

MYXWM A IER/v6 41 Unite BRUSH SEAL AND THE LIKE Application March 18, 1954, Serial No. 417,130

10 Claims. (Cl. 288-2) This invention relates as indicated to a novel brush seal or similar element wherein a specially formed and treated brush element is adapted for use as a seal against dirt, dust, moisture and the like.

' In the co-pending application of Ruben 0. Peterson and Fletcher C. Miles, Serial No. 595,422, filed May 23, 1945, now Patent No. 2,672,640, there are disclosed certain methods for the manufacture of brushes and the like wherein plastic brush bristle material is joined toa plastic base portion, ordinarily preferably a relatively thin flexible sheet or strip. In one preferred embodiment, a bundle of such plastic bristles is tightly held while compatible molten plastic is intruded into one end of such bundle to interfuse the ends of the plastic strands therewith and thereby form a unitary continuous base in which the bristles merge. The present invention is concerned with a special form of brush element which may be produced in a generally similar manner and treated to afford the desired properties. I

It is a principal object of this invention to provide novel brush seals for closures, bearings and the like which will readily permit relative movement, and especially relative rotative movement between parts of a structure or mechanism and yet maintain a most effective seal ,to exclude air, moisture, dirt, etc.

Another object is to provide such seal in the form of an elongated flexible strip to facilitate installation and mounting of the same.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a side view of a strip of my new sealing element;

Fig. 2 is a somewhat diagrammatic longitudinal section through a single strand or bristle of such element;

Fig. 3 is a transverse cross-section taken on the line 3-3 on Fig. 2;

Fig. 4 is a side view of a circularized length of sealing strip of the type shown in Fig. 1 retained within an annular channelform sheet metal back;

Fig. 5 is a transverse cross-section taken on the line 55 on Fig. 4;

Fig. 6 shows my new element employed as a bearing seal for a rotating shaft;

Fig. 7 is a longitudinal section taken on the line 7 -7 on Fig. 6;

Fig. 8 is a view generally similar to Fig. 7 but showing a modified form of seal;

7 Fig. 9 is an enlarged section through such latter seal; and

rates Patent 2,878,048 Patented Mar. 17, 1959 Fig. 10 shows an element in which the strands are slightly crimped.

Referring now more particularly to said drawing, the brush material employed in accordance with my invention may be of the general type disclosed in my co-pending application Serial No. 58,670, filed November 6, 1948, now U. S. Patent No. 2,682,734, and may comprise a wire core 1 encased in a plastic sheath or coating 2. While such wire core may, for example, be of hard steel wire (severe quench and a minimum draw back), beryllium copper wire, stainless steel wire, Z nickel wire (hard drawn, heat treated, relatively pure nickel), it may for my present purpose frequently be of a softer metal such as copper, brass, bronze and aluminum alloy.

The plastic coating material employed will be selected in accordance with operating conditions expected to be encountered, and preferred examples include nylon (polyamide resins), vinyl plastics (vinyl polymers and copolymers), and trifluorochloroethylene polymer. Other plastics such as Neoprene (polychloroprene) and Hycar (modified copolymers of butadiene and acrylonitrile) as Well as rubber and melamine resins (melamine-formaldehyde reaction products) may be employed in some cases, particularly when compounded to exhibit properties similar to nylon.

It will be understood that in employing such plastics the same will commonly have included therewith suitable fillers as well as the usual vulcanizing agents or the like to produce the resilient plastic composition for my purpose.

The thin plastic coating may be applied to the stranded material by extrusion or any other suitable method. When employing wire brush material, plastic compounds such as those having a Neoprene base may, if desired, have their bond to such brush material improved by first applying a cement to the material, such cement preferably comprising a synthetic rubber and resin composition such as is commercially available under the name of Ty-Ply-S (Vanderbilt). The material should then be properly dried before applying the plastic coating material.

When nylon is employed as the coating material 2, it will ordinarily be preferred first to coat the wire 1 with a thin film of an Epon resin which serves to bond the nylon much more effectively to the wire. Such resin is a condensation polymer containing the epoxide group and is compatible with the nylon, bonding therewith when the nylon is applied at 510 F. and setting without frothing since no volatiles are involved. It is commercially available from Shell Chemical Company (see booklet Epon Resins).

The brush bristle material 3, ordinarily in the form of straight parallel densely compacted strands, will have a small amount of a compatible molten plastic material applied to the ends of such strands to melt and interfuse the latter as well as intruding a short distance therebetween. Consequently, the strands 3 (which may be entirely of plastic or of plastic coated material such as wire or glass fiber, for example) will be integrally joined to a thin flexible base strip or sheet 4 of such plastic and the end portions of the strands will, moreover, be slightly inset in a portion of the applied molten plastic which is intruded, partly through capillary action between the densely packed strands, to form supporting sockets therefor. The plastic of such strip 4 will normally be the same as that comprising strands 3 of the plastic coat ings of such strands but may be another compatible plastic adapted when molten to interfuse therewith. .Reference may be had to my co-pending application Brush and Brush Material, Serial No. 416,989, filed March 18, 1954, now Patent No. 2,817,818, for examples of various brush-like articles suitable for my purpose.

Referring now more particularly to Figs. 4 and 5 of the drawing, a length of brush strip of the type generally shown in Fig. 1 may be mounted Within a circularized channelform sheet metal back with the bristle material 3 extending generally radially outwardly therefrom. While such back may be provided with inwardly projecting teeth or the like to assist in retaining the brush element therewithin, this is ordinarily not necessary as the strip 4 may be cemented in place and, moreover, the sides 6 and 7 of the channelform back 5 will ordinarily be turned in to embrace and secure the strip 4 and also laterally to compact the strands or bristlm 3 which otherwise Will be considerably less dense at the outer periphery of the element due to their radial disposition. Plastic strip 4 may desirably 'be of a thickness to afford appreciable transverse rigidity, assisting in thus securing the same within the channelform back through the clamping action of the sides 6 and 7 of the latter. Even when thus transversely rigid across a relatively narrow width, strip 4 may retain ample longitudinal flexibility in a relatively long length of the same to facilitate circularization, etc., as shown.

Now referring more particularly to Figs. 6 and 7 of the drawing, my new seal is shown employed as a bearing seal with a circular channelform base or back 8 press fitted or otherwise closely held within the journal 9 of the bearing adjacent the ball race 10 which forms the bearing proper for the shaft 11 rotatably supported in such journal. Since in this embodiment the channelform back 8 is circularized with the channel opening radially inwardly instead of radially outwardly as in Fig. 4, the sides of such channel will normally flare slightly outwardly to accommodate the more densely compacted strands or bristles 3.

In order to maintain such seals in good condition for long period of use and to increase their resistance to the passage of liquids and gases as well as dirt particles and the like, I utilize the capillary effect of the densely packed strands to absorb a suitable liquid, for most applications preferably a silicone although various petroleum lubricating oils and the like may likewise be utilized.

In Fig. 8 I show a similar bearing provided with a modified form of seal comprising two such circularized brushlike elements, one 12 being generally similar to element 8 and the other 13 being generally similar to that of Fig. 4. They are joined together, back-to-back, to form a fluid tight joint and are also somewhat inclined to each other so that the strands lie at an angle to the respective surfaces to be sealed. Consequently such strands are better able to flex to conform to such surfaces without buckling or separating. The composite seal is easy to insert in use, yields when necessary, and prevents passage of contaminants past the back of the seal as sometimes happens when ordinary seals are not properly seated. The ends of the strands are trimmed on a bevel, as shown, normally closely to engage such surfaces.

As shown diagrammatically in Fig. 10, the strands or bristles 14 may be slightly crimped to facilitate intrusion of the molten plastic between their ends to form base sheet 15, thereby insetting the basal portions of the strands in what are in eflect sockets as well as merging the extreme ends with such base, and to permit a degree of compacting of the strands of the seal in use. The degree of crimp should be slight so that the voids or interstices will readily retain the silicone or other lubricant.

In addition to the employment of plastic strands and plastic coated wire, glass fiber, and the like, I may employ metallic wire monofilaments integrally joined to a metal sheet base. Thus, fine copper wire may be embedded in a copper sheet of strip and treated with a silicone or mineral lubricating oil to produce one form of seal in accordance with my invention. While wire as large as .012 inch in diameter may sometimes be utilized, I ordinarily prefer to employ wire .005 inch in diameter and smaller. Such fine strands packed closely together afford good capillary 4 action and lubricant or other liquid retention even when slightly crimped.

For many sealing purposes, the retained sealing liquid should be water-repellent, non-drying, a lubricant, and have a viscosity stable over a wide temperature range. The silicones are excellent examples of such materials and they are preferred by me in many cases. Liquid silicone resins (poly-dimethyl-siloxane) are obtainable from Dow Corning Corporation and various silicone fluids and liquid lubricants are described in the latters Dow Corning Silicone Notebook, Fluid Series No. 3, issued September 1948. The degree of fluidity desired may vary widely, the densely packed fine straight strands or filaments ordinarily being more suited for the retention of light liquids and the crimped larger filaments more suited when a more viscous fluid is employed. Polymers including from about -200 dimethyl-siloxane groups are generally suitable although a highly viscous polymer having approximately 400 such groups may on occasion be utilized.

In addition to bearing seals and the like, my new treated brush-like elements may be employed as .dust seals and as seals for closures and rotative mounts such as those for aerial gun turrets.

As indicated above, reference may be had to my copending application Serial No. 58,670, now U. S. Patent 2,682,734, dated July 6, 1954, for examples of suitable plastic coated hard core materials, although for purposes of the present invention wire cores of relatively soft materials may often be employed. The plastic coating may ordinarily comprise at least 50%, by volume, of the composite strand. While the wire core may lend stiffness and resilience, the plastic coating not only serves as a means of joining the wire to the base but also assists in protecting the same from corrosion and in damping vibration.

The silicone will usually be selected to have a rather high surface tension While retaining fluidity under both high and low temperature conditions. It should wet the strands and form a barrier to liquids and gases which are to be kept out. The water-repellent characteristic of the silicones is additionally useful in this respect. Furthermore, when desired, a cooling liquid such as a silicone, water, or a mineral oil, as the case may be, may be circulated in the region contiguous to the sealing element to cool both the seal and the part protected thereby such as a shaft hearing or other travelling or moving part.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A brush type sealing element comprising a thin narrow longitudinally flexible plastic strip, densely laterally compacted straight parallel adjacent strands of compatible plastic material secured to said strip and extending therefrom, the ends of said strands being integrally merged with the material of said strip, means laterally supporting said strands to maintain the same thus densely laterally compacted in close side-by-side contact throughout their length and a liquid silicone coating said strands and retained thereby by capillary action in the elongated interstices between said strands.

2. A brush type sealing element comprising a longitudinally flexible backing strip, a body of straight densely laterally compacted filaments secured to said strip and extending therefrom in uniform side by-side engagement throughout their length, said filaments forming small capillary passages therebetween effective to imbibe .and retain a liquid, supporting means laterally :supporting said filaments to maintain the same thus densely compacted, and a thermally stable, non-drying, water repellent liquid coating said filaments and retained thereby through such capillary 'action, said filaments being thus densely compacted throughout their length.

3. A brush type sealing element comprising a backing strip, straight generally parallel densely laterally compacted filaments secured to said strip and extending therefrom, said filaments forming small capillary passages therebetween effective to imbibe and retain a liquid, supporting means laterally supporting said filaments to maintain the same thus densely compacted, the body of said filaments being trimmed to present a beveled end face adapted to engage a surface to be sealed with said filaments inclined at an angle to such surface, and a liquid coating said filaments and retained thereby through such capillary action.

4. A brush type sealing element comprising a longitudinally flexible backing strip, slightly crimped densely laterally compacted adjacent filaments secured to said strip and extending side-'by-side therefrom in close uniform contact with adjacent filaments throughout their length, adjacent contacting filaments forming small capillary passages effective to imbibe and retain a liquid, supporting means laterally supporting said filaments to maintain the same thus densely compacted, and a thermally stable, non-drying, water repellent liquid coating said filaments and retained thereby through such capillary action.

5. In a seal assembly having a surface to be sealed and a brush type sealing element engaging the same; a sealing element comprising a support, and a body of densely laterally compacted filaments secured thereto and extending therefrom, said body of filaments being trimmed to present a beveled end face parallel to and engaging said surface, with said body of filaments correspondingly inclined to said surface with adjacent filaments of said body extending side by-side from said support to said surface.

6. In a seal assembly as defined in claim 5, a liquid coating said filaments to enhance their sealing effect.

7. A circular brush type sealing element comprising a circular backing element, a large number of densely laterally compacted filaments secured to said backing element and extending generally radially outwardly therefrom in close uniform side-by-side contact with adjacent filaments throughout their length, said filaments forming small capillary passages therebetween effective to imbibe and retain a liquid, supporting means laterally supporting said filaments to maintain the same thus densely compacted; another circular brush type sealing element mounted within the aforesaid brush type sealing element and comprising a circular backing element, a large number of densely laterally compacted filaments secured to said latter backing element and extending generally radially inwardly therefrom in close uniform side-by-side contact with adjacent filaments throughout their length, said latter filaments forming small capillary passages therebetween effective to imbibe and retain a liquid, supporting means laterally supporting said latter filaments to maintain the same thus densely compacted, and means joining said backing elements effective to prevent passage of fluid therebetween.

8. The seal of claim 7, wherein each said element is inclined toward the other.

9. The seal of claim 7, wherein each said element is inclined toward the other and the ends of said filaments are trimmed on a bevel to bring the peripheral faces of said respective elements into substantial parallelism to each other.

10. The seal of claim 7 impregnated with a liquid retained thereby through capillary action.

References Cited in the file of this patent UNITED STATES PATENTS 885,032 De Ferranti Apr. 21, 1908 1,042,719 Pease Oct. 29, 1912 2,274,234 Ekkebus et al Feb. 24, 1942 2,388,867 Peterson Nov. 13, 1945 2,672,640 Peterson et al Mar. 23, 1954 FOREIGN PATENTS 10,839 Great Britain 1905 421,302 Italy Mar. 20, 1947 680,233 Great Britain Oct. 1, 1952 

